1. Field of the Invention
This invention relates to flattening polishing devices and flattening polishing methods for flatly polishing plated films or insulating films formed on, for example, wafer surfaces.
2. Description of the Related Art
FIGS. 10A to 10F show sectional side elevation views illustrating manufacturing processes for a metal interconnection type board.
An interconnection pattern 2 composed of copper (Cu) is formed on a surface of a wafer 1 composed of silicon so as to coat the surface of the wafer 1 including the interconnection pattern 2 with an insulating film 3 composed of silicon dioxide (SiO2) (FIG. 10A).
Further, conducting holes 4 for a laminated interconnection pattern are etched to be formed in the insulating film 3 (FIG. 10B), so as to coat the surface of the insulating film 3 including inner surfaces of the conducting holes 4 with a barrier film 5 composed of tantalum (Ta) or titanium (Ti) or the like (FIG. 10C), and seed films 6 composed of copper (Cu) are formed by sputtering(FIG. 10D). Further, a film 7 for the laminated interconnection pattern composed of copper (Cu) is plated in a comparatively thick condition and is formed in such a manner that inner portions of the conducting holes 4 are completely blocked (FIG. 10E). Thereafter, unnecessary films 7 for the laminated interconnection pattern on the barrier film 5 are machined to be polished so as to remove them and a laminated interconnection pattern 8 is formed so as to have a final metal interconnection type board 9 (FIG. 10F).
FIG. 12 shows a sectional side elevation view illustrating a manufacturing process for an element separation type board.
Elements 12 are formed on a surface of a wafer 11 composed, for example, of silicon so as to coat the surface of the wafer 11 containing the elements 12 with stopper films 13 composed of silicon nitride (SiN). Further, element separating trench holes 14 are etched to be formed from the stopper films 13 over to the wafer 11 so as to coat the holes, in a relatively thick condition, with an insulating film 15 composed of silicon dioxide (SiO2) in such a manner that an inner portion of the trench holes 14 are completely blocked (FIG. 12A). Thereafter, unnecessary insulating films 15 on the stopper films 13 are machined to be polished so as to remove them and trenches 16 are formed so as to have the final element separation type board 17 (FIG. 12B).
In a polishing process, when manufacturing the above respective boards 9 and 17, the flattening polishing device is used.
FIG. 14 shows a perspective view illustrating an outline of a related flattening polishing device.
This flattening polishing device 20 is provided with a rotatable surface plate 22 in a shape of a disk on a top face of which a polishing cloth 21 is stuck, a rotatable and vertically (along the Z axis) movable mounting plate 23 in a shape of a disk for holding wafers 1 and 11 by bottom faces thereof and a nozzle 24 for supplying a polishing liquid P on the polishing cloth 21.
In such constitution, first, the surfaces of the wafers 1 and 11 on which the films 7 and 15 are formed are faced downward, a reverse face of the wafer 1 is bonded or is vacuum-adsorbed to the bottom face of the mounting plate 23. Next, while the surface plate 22 and the mounting plate 23 are rotated, the polishing solution P is supplied on the polishing cloth 21 from the nozzle 24. Further, the mounting plate 23 is lowered, the surfaces of the wafers 1 and 11 are forcedly pressed on the polishing cloth 21 so as to polish the films 7 and 15 formed on the surfaces of the wafers 1 and 11.
In an initial stage of the polishing process on the occasion of respectively manufacturing the above described boards 9 and 17, only a kind of film that is respectively the film 7 for the laminated interconnection pattern or the insulating film 15 may well be polished. However, in the final stage, since it is respectively necessary to expose the barrier film 5 or the stopper film 13, two kinds of films should concurrently be polished, that is, not only the film 7 for the laminated interconnection pattern or the insulating film 15, but also the barrier film 5 or the stopper film 13.
When the films of different kinds, in other words, the films of different hardness are polished using the related flattening polishing device 20, there are such cases where defects such as dishing, erosion (thinning) recess, scratch, chemical damage, overpolishing, and underpolishing are formed.
FIG. 11 shows a sectional side elevation view illustrating defects in the metal interconnection type board 9 and FIG. 13 shows a sectional side elevation view illustrating defects in the element separation type board 17.
FIG. 11A and FIG. 13A are examples of the dishing, wherein at central portions of the film 7 for the laminated interconnection board and of the insulating film 15 over broad areas are caved in due to too much polishing so as to result in a shortage of sectional areas for the laminated interconnection pattern 8 and the trench 16, to eventually become the defects.
FIG. 11B and FIG. 13B are examples of the erosion (thinning), wherein portions whose pattern density are high are caved in due to excessive polishing so as to result in a shortage of sectional areas for the laminated interconnection pattern 8 and the trench 16, to eventually become the defects.
FIG. 11C and FIG. 13C are examples of the recesses, wherein a side of the laminated interconnection pattern 8 and a side of the trench 16 are lowered at boundaries between the laminated interconnection pattern 8 and the insulating films 3 and between the trench 16 and the stopper film 13 so as to generate level differences, to consequently become defects.
FIG. 11D is an example of the scratch or the chemical damage, wherein an open circuit or short circuit or a failure in a resistance value of the laminated interconnection pattern 8 is generated, to eventually become faults.
FIG. 13D is an example such as the overpolishing and the underpolishing, wherein due to a shortage in relation to a set removal amount of the insulating films 15, the insulating films 15 remain on the surface of the board to consequently become defects, or due to an excessive amount in relation to the set removal amount of the insulating films 15 the sectional area of the trench 16 results in shortage to eventually become defects.
The present invention is planned and constituted according to the above-described circumstances, and it is an object of the present invention to provide a flattening polishing device and a flattening polishing method capable of conducting a flattening polishing with high accuracy and no defects.
In the present invention, and in the flattening polishing device for flatly polishing a surface of an object to be polished, the above-described object can be attained by providing the device with first polishing means and second polishing means which are coaxially disposed, moving means for moving the respective polishing means relative to each other in an axial direction and rotary means for rotating the respective polishing means around a shaft.
Further, in the present invention, and in the flattening polishing method for flatly polishing a surface of an object to be polished, the above-described object can be attained by providing the method with a process for rotating two polishing means disposed in shapes of concentric circles, a process for protruding a polishing surface of one of the polishing means more than a polishing surface of the other polishing means to a side of the object to be polished, a process for polishing the surface of the object to be polished by one of the polishing means, a process for protruding the polishing surface of the other polishing means more than the polishing surface of the one of the polishing means to the side of the object to be polished and a process for polishing the surface of the object to be polished by the other polishing means.
According to the above-described constitution, since the two polishing means are arranged coaxially, the device can be made in compact size without any need for installation of a plurality of large surface plates as in the related device. Further, since the object to be polished can be machined in multi-steps by one chuck, variations in machining accuracy due to rechucking can be suppressed. Furthermore, since fixed size and highly efficient machining or fixed pressure and highly graded chemical machining can be carried out in multi-steps, it is possible to machine the object to be polished with no defects.
Further, in the case of polishing process for compound semiconductor, two-step polishing is performed with liquid polishing agents changed. A series process for performing two-step polishing and a parallel process for performing one-step polishing in parallel can therefore be selectively carried out in one polishing device.